1. Field of the Invention
This invention relates to container components and more particularly to an improved method and apparatus for forming and construction of a digitally openable container component such as an end closure that can be formed from sheet metal having a protective coating on the surface thereof which is to be the non-public surface of the closure without adversely affecting the integrity of the coating during the forming operation. The container component which is thus formed can be sealed on containers for soda pop or the like which may be corrosive to metal without repair coating the non-public surface of the component.
2. Description of the Prior Art
Many millions of the so-called easy opening can ends are used each year for cans of soda pop and other beverages. Most of these easy opening can ends are of the pull tab type with an integral rivet connecting the tab to a severable tear strip. In recent years, these container ends have been criticized because of their having a removable tear strip portion, and the propensity of consumers to indiscriminately dispose of tab and tear strip immediately following their separation from the container. In part, the problems attendant such indiscriminate tab disposition has resulted in the actual or contemplated banning of such closures in certain jurisdictions. An easy opening container end is therefore desired which has no severable tab and tear strip to be indiscriminately discarded. Preferably, such tabless container ends should be suited for use with all kinds of beverages and should be adapted to be formed from precoated sheet without the need for repair coating the formed container closure.
The prior art and notably the patented art, is replete with many suggested expedients for achieving the long desired objective of simplified can opening, including several suggested expedients for can closures that can be digitally opened, i.e., manually opened without the use of auxiliary tools or the like. Included in such expedients are the use of container walls and end closures which include weakening lines or score lines defining tear strips or panels which can either be depressed into or pried out of a container to form either a vent or a pouring opening therein. Closures of this type are exemplarily disclosed in a number of U.S. Pat. Nos. including Newman 1,805,003, Fried 2,176,878, Asbury 3,227,304, Asbury 3,246,791, Asbury 3,355,058, Klein et al. 3,334,775, Foss et al 3,401,436, Punte 2,187,433, Punte 2,289,452, Punte 2,312,358, Punte 2,312,359, Fink 2,119,533, Punte 2,120,186, Geiger 3,362,569 and Klein 3,779,417. Such end closures have sometimes required the use of rigid tools, such as a coin or a fork, to rupture the score line around the removable panel in order to form an opening in the end closure. Several of such end closures have included embossments in the removable portion to facilitate opening of the removable portion by pressing or prying against such embossments.
Metal container ends for easy opening cans for corrosive contents such as carbonated soft drinks, fruit juices and the like usually have a protective coating on the interior or non-public surface of the container end to protect the metal from the container contents. When the container ends are formed from coated sheet, forming the score lines or weakening lines in container ends sometimes fractures or breaks the coating and expose bare metal to the container contents which can corrode the metal and cause perforations through the container end closure. Easy opening container ends have therefore sometimes been repair coated to insure that no bare metal is exposed after the weakening line has been formed. It is also known to provide improved coating systems which resist fracture or cracking of the coating during the forming operation as is disclosed in U.S. Pat. No. 3,632,461. Methods and tools are also known for forming weakening lines or score lines in can ends without adversely affecting the integrity of the protective coating on the ends as is disclosed in a number of U.S. Pat. Nos. including Schrecker 3,688,718, Franek et al. 3,687,099 and Cookson 3,698,590 among others. However, all of these methods have been adapted for forming score lines in easy opening container walls which have pull tabs or the like attached to the severable tear strips to facilitate severance of the score lines. The methods and apparatus disclosed in such patents are not adapted for forming tabless container components in which the score lines or weakening lines may be severed by digitally applied pressure. Other prior art disclosures of interest relative to methods and tools for forming weakening or score lines are contained in the following U.S. Pat. Nos. Morfoot 619,259, Kennedy et al. 3,543,961, Franek et al. 3,638,825, Fraze 3,291,336, Stuchbery 3,359,773 and Saunders 3,507,418.